1. Field of the Invention
The present invention relates to ink printers and, particularly, to a printing system and method having a dot matrix-type printer using a liquid ink reservoir.
2. Description of the Related Art
Dot matrix printers (sometimes referred to as “impact matrix printers”) are well known in the art. A dot matrix printer is a type of computer printer with a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a typewriter. Unlike a typewriter or daisy wheel printer, letters are drawn out of a dot matrix, and thus, varied fonts and arbitrary graphics can be produced.
FIGS. 2A and 2C illustrate a conventional dot matrix printer head 100. The rear end of member 11 is provided with an upwardly projecting wall 14, as shown, having a plurality of tapped openings 15. The rearwardly directed surface of wall 14 has a truncated pyramidal configuration. The openings 15 provided on the rear surface are aligned so as to be substantially perpendicular to their associated mounting surfaces.
Each of the openings is tapped to threadably engage the threaded collar 17 of a solenoid assembly 18. FIG. 2B shows a cross-sectional view of one solenoid assembly 18 removed from the assembly 10 in order to show the internal structure in detail. The remaining solenoid assemblies are similarly provided with threaded collars for threadably engaging an associated one of the tapped apertures 15. Each solenoid has a slender solenoid wire 19 projecting outwardly through an opening provided at the forward end of each tapped collar 17, from which print wires extend from the forward end of each solenoid assembly to the forward or left-hand end of member 11.
Die cast member 11 is further provided with a first mounting portion 20 having a first groove 21 provided in a first upright portion 22 and a groove 21a provided in a second upright portion 24. The grooves 21 and 21a are adapted to receive a flat plate 25 provided with a plurality of openings 26, each receiving an associated one of the solenoid wires 19.
A second supporting section 27 die cast as an integral part of member 11 and positioned in front of section 20 is comprised of a first groove 28 extending from a first upright portion 29 and a second groove 28a provided in a second upright portion 30. These grooves are adapted to receive a flat plate 31 provided with a plurality of openings 32, each receiving an associate one of the solenoid wires 19.
A final upright portion 34 is die cast as an integral portion of member 11 and is provided with a centrally located opening 35, with the opening widening at ledge 38 to form a wider opening 39. In operation, the solenoid wires 19 may be selectively moved in the directions shown by arrows 40 and 41 (as shown in FIG. 2D) so as to selectively impact against a paper tape (not shown) positioned in close proximity to the front end of the printer head assembly. In order that the constant and rapid movement of the print wires be subjected to a minimum amount of abrasive wear, a plurality of tube guides 42 are provided. Each of the tube guides 42 is comprised of a hollow, elongated sleeve formed of a metallic material which is force-fitted through an associated opening 26 in disc 25 and which receives a print wire through its central opening so as to prevent any abrasive wear between the solenoid wires and the disc 25.
FIG. 2B shows a detailed sectional view of one of the print wire solenoids 18, which includes a one-piece shell member 50 whose right-hand portion is substantially cylindrical in shape and is threaded at 17. A fastening nut 51 threadably engages threaded collar 17 for the purpose of tightening or locking the solenoid to the upright wall 14 once the solenoid is mounted in the desired position. The left-hand portion of shell 50 is also cylindrical in shape and has a cylindrical wall 53 to form a hollow annular shaped interior region 54 which houses the solenoid coil 55. The central core portion 52 has a centrally located opening 56 for slidably receiving print wire 19 which is secured to the left-hand end of cylindrical shaped armature member 57 and which passes through opening 56 to a wider opening 56a and a still wider opening 56b provided in shell 50. A tubular shaped wire guide 58 surrounds a portion of print wire 19, as shown. The solenoid coil 55 is provided with a pair of connecting leads 59 for coupling the print solenoid to driving circuitry. The connecting leads 59 extend through an opening 60 provided near the left-hand end of shell 50.
The armature member 57, which is formed of a permanent magnet material, is secured to a circular shaped disc 61, formed of a springy or resilient metallic material, by means of rivet 62. A thin wafer 63 is positioned between armature 57 and the left-hand surface of spring 61 and a second wafer 64 is positioned between the right-hand surface of spring 61 and the head of rivet 62, to reduce vibration.
A relatively thick disc shaped member 65, having a central opening 65a, is positioned within shell 50 and has a continuous annular shaped projecting flange portion 65b engaging the left-hand surface of spring 61. The armature assembly, including spring 61 and armature 57, as well as disc 65, is rigidly secured within shell 50 by means of a cap 66 having a tapped interior surface 67 which threadably engages the threaded portion 68 of shell 50.
In operation, with the coil assembly 55 de-energized, spring 61 assumes its flat shape, as shown in FIG. 2B. Upon energization of coil assembly 55, the magnetic field generated by coil 55 urges armature 57 in a direction shown by arrow A against the biasing force imposed upon the armature by spring 61 thereby moving print wire. When the coil assembly 55 is de-energized, armature 57 is caused to return to the position shown in FIG. 2B under the influence of the biasing spring 61. The print solenoid is adjusted so as to cause the print wire to move approximately 0.45 to 0.56 mm toward the right when the coil assembly is energized, thereby causing the extreme left-hand end of the print wire to extend by the above-mentioned distance in order to impact a ribbon (not shown) and thereby print a dot upon a paper document supported by a platen (not shown).
The coil assembly is wound upon a cylindrical shaped bobbin 70, which is then inserted into the hollow annular portion 54 of shell 50. The tubular shaped wire guide 58 has its left-hand portion secured to the interior opening 56a by means of a suitable epoxy. An epoxy is also preferably applied between the threaded portion 68 of shell 50 and the tapped portion 67 of cap 66 in order to firmly join the shell 53 and cap 66 after appropriate adjustment (i.e., tightening) of cap 66 upon the shell. A small opening 66a is provided at the center of cap 66 to adjust the amount of travel which the armature 57 may experience and to thereby control the amount of travel experienced by each print wire 19.
Printer head 100, shown in FIGS. 2A-2D, is a conventional dot matrix printer head. As seen from the above, there is great mechanical complexity, on a very small scale, required to form a sequence of dots (to form characters or graphics) on a piece of paper. Misalignment of any one element will cause misalignments of the connecting parts, thus making printer head 100 highly susceptible to damage. A dot printer head with a minimum of interlinking, complex parts would be desirable.
Thus, a printing system and method solving the aforementioned problems is desired.